A Selective Catalytic Reduction (SCR) module is typically provided in an aftertreatment system of an engine to remove or reduce nitrous oxides (NOx) emissions in an exhaust gas flow. SCR systems use one or more reductants, such as urea solution, that are introduced into the exhaust gas flow.
Mixing elements are generally used in engine aftertreatment systems to enhance mixing of the reductant and the exhaust gas. However, known mixing elements may be unable to uniformly distribute the reductant within the exhaust gas. Further, during the mixing, the reductant may contact and form deposits on surfaces of the mixing element and/or an exhaust conduit. The reductant deposits may crystallize and block passages of the mixing element and/or the exhaust conduit of the aftertreatment system. Also, the mixing elements may provide low evaporation rates, low uniformity and/or imbalance of the reductant on a downstream side of the mixing element, causing/resulting in increased back pressure across the mixing element and so on.
In some exhaust systems, the blockages may be prevented by a regeneration process in which the mixing element is heated to burn away the deposits. The regeneration process requires an additional heating arrangement to be provided on the mixing element. Further, the regeneration process may require a stipulated amount of time for completion and additional power consumption leading to reduction in overall system efficiency. The formation of deposits may lead to material wastage resulting in increased operational cost. Hence, there is a need for an improved mixing element for mixing of the two or more fluids in the aftertreatment applications.
U.S. Pat. No. 721,973 discloses a combination of a conduit through which a fluid flows and a rotary propeller wheel located within the conduit in the path of the fluid. The propeller wheel is actuated by the movement of the fluid. An agitator or a mixer is located within the conduit in the path of the fluid and in advance of the propeller wheel. The agitator is connected with and actuated by the propeller. The agitator is of less area or offers substantially less resistance to the fluid than the propeller.